Nitrate levels in edible wild herbs and vegetables common in Jordan.

Forty six selected species of wild edible herbs and vegetables common in Jordan were collected from their natural growing places; twelve of them were collected from more than one location. The nitrate contents of the edible parts, and in some cases non-edible parts, were determined using the cadmium reduction method. The nitrate level varied widely ranging from 29 mg/kg in the leaves of tetragonolbus (Tetragonolobus Palaestinus) to 6743 mg/kg in star fenugreek (Trigonella Stellata). With the exception of the families of Araceae and Cruciferae, there was a wide variation in the nitrate concentrations within the species of each family. In general, the nitrate content of the stems was higher than that of the leaves which in turn was higher than that of the roots and bulbs. The same species collected from irrigated (presumably fertilized) farms were generally of higher nitrate content than those collected from pasture, forest or non-irrigated farms. However, many of the studied plants remain of relatively high nitrate content regardless of where they were grown.